Lifting truck



P 1939. c. s. SCHROEDER'. 2,173,068

LI FTING TRUCK Original Filed June 7, 1935 4 Sheets-Sheet '1 Sept. 12,1939. c. s. SCHROEDER LIFTING TRUCK 4 Sheets-Sheet 2 Original Filed June7, 1935 Sept. 12, 1939 .c. s. SCHIIROEDER LIFTING TRUCK Original FiledJune 7, 1935 4 Sheets-Sheet 3 gwventoz c. s. SCHROEDER 2,173,068

LIFTING TRUCK Sept. 12, 1939.

Original Filed June 7, 1955 4 Sheets-Sheet 4 mi N Patented Sept. 12,1939 UNITED STATES PATENT OFFICE LIFTING TRUCK necticut Originalapplication June 7, 1935, Serial No.

Divided and this application December 11, 1936, Serial No. 115,282

4 Claims.

This invention relates to industrial trucks of the type utilized forcarrying heavy industrial loads.

An industrial truck of the type adapted to carry 5 extremely heavy loadsmust be designed so that in moving over relatively rough terrain orrough floors, the load supporting wheels will remain continuously incontact with the floor or terrain despite the variations in the same. Itis also of importance in a truck of this type to maintain the loadstable and against tilting, especially where the load is necessarilyelevated to a particularly high position or has a high center ofgravity. It is also necessary in a truck of this type to maintain thetractive wheels in proper relation to the terrain so as to obtain allthe traction necessary. It is also advantageous to so design the truckthat in carrying the heavy loads, the weight will be so distributed asto eliminate torsional stresses in the frame.

It is naturally possible to obtain the greatest stability of the load bysimply having the truck supported by wheels solidly secured to the loadcarrying portion and to the rear or driving por- 5 tion of the truck. Itwill be helpful if at this point it is explained that the rear ordriving portion of an industrial truck is usually the part having thebattery compartment, the operators platform and the driving wheels. Theforward por- 30 tion of the truck is referred to as the load carryingportion, and in a fork truck, the forks normally overhang the forwardportion. Naturally, in a truck in which the wheels are solid with theload carrying and driving portions, great tor- 35 sional stresses willbe set up in the frame where the terrain is rough, since certain of thewheels will be lifted entirely from the terrain should it be suincientlyrough, and three wheels will determine the plane of support. For thisreason,

40 the tractive efiort of the driving wheels will also be interferedwith under the same conditions.

As distinguished from the type of truck described in the precedingparagraph, we can visualize a truck in which the wheels carrying the 45load supporting portion are articulated relatively to the loadsupporting portion so that the wheels may follow the terrain mostaccurately, and we can further visualize the rear or driving wheelssimilarly placed on the truck. It will be readily to appreciated that ina truck of this type, we will have the maximum possible tractive efiort,and we will also have a minimum of stress set up in the frame. However,this type of truck will have absolutely no load stability and cannot beuti- 55 lized. It is in between the two diametrically oppositeconstructions just described that we find present day commercialindustrial trucks, and therefore we naturally find a compromiseconstruction.

In order to obtain substantial stability while 5 eliminating framestress, and in order to' obtain the proper tractive effort, industrialtrucks now generally utilize articulating load supporting wheels and/orarticulating load supporting axles. The rear driving mechanism isgenerally supported by means of springs which'c'ontribute the necessarystability to the truck. More conservative types of construction, wherestability is exceedingly important, utilize supporting wheels mounted onbeam members which articulate only '1 on a transverse axis relatively tothe truck. Naturally, even such trucks, when loaded, do not have as higha load stability as is desirable.

I believe that I have invented an industrial truck which embodies anextreme departure from 20 the teachings of the prior art, whereby Iobtain a truck in which the construction is not a compromise along thelines discussed above. I utilize a load supporting portion supported bywheels mounted solidly on this load supporting portion. I then utilize adriving portion which I connect to this load supporting portion by meanspermitting'a sliding, and preferably an articulating, pivoting movementof the load supporting portion relatively to said driving portion. Inthis way, my load wheels follow the terrain quite well While at the sametime contributing maximum load stability.

My truck should not be confused with tractor trucks in which a completetruck unit having front and rear wheels supports at one end a twowheeled or four wheeled trailer. While my truck is formed of two units,those two units cooperate to form a single truck, rather than a truckand trailer. 40

Preferably, the means which I utilize for obtaining this sliding andarticulating movement comprise a pivot shaft connecting the loadsupporting portion to the driving portion, and about which pivot the twoportions rotate relatively to one another. Preferably, also, the twoportions of the truck terminate in vertical plates which form thesliding or rotating surfaces, there being bolt and slot members forlimiting the movement between these two plates to a predetermineddegree. Naturally, these pivots, bolts, and slots might conceivably beutilized without the presence of the main pivoting shaft, but I believethat my particular construction is better.

It will be especially interesting to note that I find that the locationof this pivot shaft should be at a very low point and preferably almostin the same plane as the axis of rotation of the load supporting wheels.

It will also be interesting to note that with the pivot shaft located atthis lowest possible point, when the truck is loaded, there will be atendency to separate the truck portions at their upper point, thustending to bend the pivot shaft. This bending action is, of course,resisted by. a plurality of bolts and slot members connecting the twovertical plates.

The particular construction indicated is especially useful in connectionwith a truck of the tilting fork type. It is a tilting fork type oftruck, therefore, which is shown in this application. The novel featuresof the tilting fork construction per se are shown and are claimed in myapplication for a Lifting truck filed June '7, 1935, Serial No. 25,437,of which this application is a division.

Having thus generally described the purposes for which my invention isespecially adapted, and having now also described the general featuresof the invention, I shall proceed with a detailed description of themechanism I prefer to utilize. I believe, however, that I have made asubstantial contribution to the industrial truck art, which contributionshould not be limited except as may be required by the state of the art.

Referring now to the drawings, Fig. 1 illustrates a truck embodying myinvention, the truck shown being of the type having tilting uprights.Fig. 2 shows the truck of Fig. l viewed from its rear end and with itsrear or driving portion tilted relatively to its front or loadsupporting portion. Figs. 3-6, inclusive, show the construction of themeans whereby it is possible to articulate the load supporting portionrelatively to the rear or driving portion. Fig. 7 is a perspective viewof the frame of the load supporting portion, while Fig. 8 is aperspective view of the rear or driving portion of the frame. Fig. 9 isa section taken through the truck to illustrate the mount ing of thepivot shaft about which the two portions pivot. Fig. 10 is a sectionshowing a bolt connecting the vertical plates of the load supporting anddriving portions.

Referring now more particularly to the drawings, and especially to Figs.1, 2, 7 and 8, reference numeral H] indicates the rear portion of thetruck while reference numeral 1 I indicates the forward or loadsupporting portion of the truck. The portion IEI carries the usualbattery and mechanism for driving the wheels, all this being quiteunnecessary to indicate in detail. It should be noted, however that therear portion l0 terminates in a vertical plate l2 having a series ofslots l3 outlined by abutments i4 and a hole I5 forming a bearing forthe pivot shaft l6 relatively to which the portions Ill and l larticulate or pivot.

The load supporting portion l l terminates in a vertical plate member Hwhich supports a series of bolts l8 protruding from abutments l9, andadapted to operate in the slots l3 of the vertical plate E2. Thevertical plate II also supports pivot shaft l6, which functions to holdthe plates I2 and I! for pivoting movement relatively to one another, asis best illustrated in Fig. 9, the shaft I6 being threaded at 20 tosupport the nut member 2| for maintaining the parts properly positioned.A lubricating nipple 22 is utilized for lubricating this bolt in theusual manner well known in the art.

In Fig. 10, the coaction of one of the bolts [8 with the parts I! and i2is also illustrated more in detail. It will be noted that the bolt I8 isthreaded as at 23 for coaction with a nut 24. The abutments I4 and IQ ofthe plates 12 and I! preferably prevent frictional contact between theplates [2 and H, the abutments acting as the rubbing and guidingsurfaces.

In Figs. 3-7, the location of the pivot shaft [6 relatively to the truckis best indicated. It will be' seen that this pivot shaft is placed atthe lowermost possible position relatively to the plate members l2 andI! and substantially in the same plane as the axis on which the loadsupporting wheels 25 rotate. While the shaft may be placed elsewhere, Ihave found this to be the best location.

The load supporting wheels 25 are carried on axles, in turn supported bypivot shafts mounted on ears 26 of the abutments 21, shown best in Fig.7. By this construction, the load wheels are fixedly carried by the loadsupporting portion, in so far as relative vertical movement isconcerned, the wheels being, of course, pivotal in the usual manner wellknown in the art, should it be desirable to steer through these Wheels.

The articulating or rotating movement between the vertical plates l2 andI I is probably best illustrated in Figs. 26, inclusive. It will benoted that the pivoting or articulating movement is limited by thelength of the slots [3, this movement being calibrated to the properamount generally required in commercial trucks. The stability of a truckutilizing this construction is easily appreciated. The load portion issupported by two load supporting wheels which accommodate themselves toany terrain. The load platform pivots easily and as a whole relativelyto the shaft it, thus allowing the accommodation of the wheels to theterrain while exerting no strain whatsoever on the frame of the truck.Similarly, the movement of the load supporting portion does not effectthe position of the drive wheels nor does it affect the tractive effortof the said wheels.

As I have already indicated, I have illustrated my invention as appliedto a truck of the tilting fork type. I shall now describe generally themounting of the tilting forks on the truck, it being understood that thedetailed construction of the tilting forks and their operation isthoroughly covered in my application supra.

A pair of uprights 30 have formed thereon horizontal portions 3|equipped with rollers 32 and 33 (Fig. l), the rollers 32 cooperatingwith guide tracks 34, while the rollers 33 cooperate with guide tracks35. Through a rack bar 36 cooperating with electrically driven pinionmechanism 31, the uprights 30 may be tilted about the rollers 33, or maybe moved forwardly and rearwardly on the tracks 34 and 35 through thecooperation of the rollers 32 and 33, as may be desired. The uprights 30carry a load platform 38 having forks 39, which platform 38 movesvertically on the uprights 30 through rollers 40, as will be readilyappreciated.

For elevating the platform 38, I use an electrically operated means 4|which operates through a chain 42 (Fig. 2) to elevate and lower theplatform in the usual manner well known in the art. It will be readilyappreciated that because the rear driving portion ID of the truckarticulates relatively to the load supporting portion l I, it isnecessary that the controls for the electrically driven pinion mechanism31 and lifting mechanism 4| be of a special nature. I have providedrather unique connections between control levers 43 and 44, the rods 45and 46, and the mechanisms 37 and 4|, all of which are covered in myapplication supra.

I now claim:

1. In a lift truck of the class described, a load supporting portionterminating in a substantially vertical plate, a driving portionterminating also in a substantially vertical plate, means for securingsaid load and driving portions with said plates back to back whereby toform a completed truck, said means being arranged to permit sliding ofsaid plates relatively to one another.

2. In a lift truck of the class described, a load supporting portionterminating in a substantially vertical plate, a driving portionterminating also in a substantially vertical plate, means for securingsaid load and driving portions with said plates back to back whereby toform a completed truck, a pivot shaft forming 'part of said securingmeans, said pivot shaft being adapted to form an axis about which saidplates may rotate relatively to one another.

3. In a lift truck of the class described, a load supporting portionterminating in a substantially vertical plate, a driving portionterminating also in a substantially vertical plate, means for securingsaid load and driving portions with said plates back to back whereby toform a completed truck, said means including a bolt moving in an areshaped slot and adapted to permit sliding of said plates relatively toone another While controlling and guiding said sliding movement.

4. In a lift truck of the class described, a load supporting portionterminating in a substantially vertical plate, a driving portionterminating also in a substantially vertical plate, means for securingsaid load and driving portions with said plates back to back whereby toform a completed truck, said means comprising a pivot shaft locatedsubstantially at the lowest point in each of said plates and about whichsaid plates may rotate relatively to one another to permit articulatingof the truck on a horizontal axis, and bolt and slot means located abovesaid axis for limiting said rotation and for maintaining said plates inassembled relation.

CHARLES S. SCHROEDER.

